The present invention relates to a semiconductor device equipped with a capacitor including a capacitor dielectric film made from a dielectric film with a large dielectric constant (hereinafter referred to as a highly dielectric film) or a ferroelectric film, and method and system for fabricating the same.
In accordance with recent trend toward a high operation speed and small power consumption of microcomputers and the like, consumer electronic equipment are highly developed, and semiconductor elements included in semiconductor devices used in the consumer electronic equipment have been rapidly refined.
As a result, unwanted radiation, that is, electromagnetic wave noise caused in electronic equipment, has become a serious problem. As means for reducing the unwanted radiation, attention is paid to a technique to involve, in a semiconductor integrated circuit device, a capacitor having large capacity and including a capacitor dielectric film of a highly dielectric film or a ferroelectric film.
Furthermore, in accordance with development of higher integration of a dynamic RAM, a technique to use a highly dielectric film or a ferroelectric film as a capacitor dielectric film of a capacitor instead of a conventionally used oxide or nitride of silicon is now widely studied.
Moreover, for the purpose of realizing practical use of a nonvolatile RAM capable of operating at a low voltage and reading or writing at a high speed, a ferroelectric film with a spontaneous polarization characteristic is now earnestly studied and developed.
Accordingly, it is significant to develop a method for realizing higher integration of a semiconductor device without degrading characteristics of a capacitor.
Now, a conventional method of fabricating a semiconductor device will be described with reference to FIGS. 11A through 11C, 12A and 12B.
First, as is shown in FIG. 11A, after forming an isolation region 11 and a gate electrode 12 of an FET on a semiconductor substrate 10, impurity diffusion layers and the like (not shown) of the FET are formed in a surface portion of the semiconductor substrate 10, and an insulating film 13 is deposited to cover the isolation region 11 and the gate electrode 12. Thereafter, on a portion of the insulating film 13 above the isolation region 11, a capacitor lower electrode 14 of a platinum film or the like, a capacitor dielectric film 15 of a highly dielectric film or a ferroelectric film and a capacitor upper electrode 16 of a platinum film or the like are formed. The capacitor lower electrode 14, the capacitor dielectric film 15 and the capacitor upper electrode 16 together form a capacitor.
Next, as is shown in FIG. 11B, after forming a first protection film 17 for covering the capacitor, a contact hole 18 of the FET is formed in the insulating film 13 and a contact hole 19 of the capacitor is formed in the first protection film 17. Then, a metal film such as a titanium film and an aluminum alloy film is deposited over the insulating film 13 and the first protection film 17, and the metal film is patterned into a first interconnection layer 20 connected to the impurity diffusion layer of the FET or the capacitor upper electrode 16. Thereafter, the first interconnection layer 20 is subjected to a heat treatment.
Then, as is shown in FIG. 11C, by plasma tetraethylorthosilicate (hereinafter referred to as TEOS) CVD, an interlayer insulating film (plasma TEOS film) 21 of a silicon oxide film is deposited over the first interconnection layer 20 and the capacitor. In consideration of planarization by reflow, the interlayer insulating film 21 is formed so as to have a thickness of approximately 1 xcexcm or more in a portion above the first interconnection layer 20 on the capacitor upper electrode 16.
Next, after planarizing the interlayer insulating film 21, a contact hole is formed in the interlayer insulating film 21, and a second interconnection layer 22 connected to the first interconnection layer 20 is formed on the interlayer insulating film 21 as is shown in FIG. 12A.
Then, as is shown in FIG. 12B, a second protection film 23 is deposited on the interlayer insulating film 21 so as to cover the second interconnection layer 22.
However, since the interlayer insulating film 21 is formed from the plasma TEOS film in the conventional structure, the interlayer insulating film 21 applies merely small stress to the capacitor and tends to be compressive. Accordingly, there arises a problem that the capacitor dielectric film 15 cannot sufficiently attain spontaneous planarization, and hence, the capacitor cannot attain good characteristics.
Therefore, the present inventors have proposed, in Japanese Patent Publication No. 2846310, a technique to use, instead of the plasma TEOS film, a silicon oxide film formed by TEOS-O3 CVD (hereinafter referred to as the TEOS-O3 film) as the interlayer insulating film 21.
When the TEOS-O3 film is used as the interlayer insulating film 21, stress applied to the capacitor can be increased, so as to improve the characteristics of the capacitor.
The use of the TEOS-O3 film as the interlayer insulating film, however, causes other problems as follows: Defects such as holes are locally formed in the interlayer insulating film of the TEOS-O3 film; and the growth rate of the TEOS-O3 film is varied depending upon the kind of underlying film.
Such problems lead to quality degradation of a semiconductor integrated circuit device, and in addition, the characteristics of the capacitor cannot be improved because stress cannot be uniformly applied to the capacitor.
In consideration of the aforementioned problems, an object of the invention is improving the characteristics of a TEOS-O3 film formed on a capacitor.
In order to achieve the object, the first semiconductor device of this invention comprises a capacitor including a capacitor lower electrode, a capacitor dielectric film of a highly dielectric film or a ferroelectric film and a capacitor upper electrode successively formed on a semiconductor substrate; a protection film formed on the semiconductor substrate over the capacitor; a first TEOS-O3 film having a relatively large water content formed on the protection film through first TEOS-O3 CVD where an ozone concentration is relatively low; and a second TEOS-O3 CVD film having a relatively small water content formed on the first TEOS-O3 film through second TEOS-O3 CVD where the ozone concentration is relatively high.
In the first semiconductor device, the first TEOS-O3 film formed on the protection film covering the capacitor is formed through the first TEOS-O3 CVD where the ozone concentration is relatively low. Therefore, the first TEOS-O3 film can attain good film quality with no defects such as holes and can be improved in its adhesion to the protection film due to its large water content. Also, since the second TEOS-O3 film is formed through the second TEOS-O3 CVD where the ozone concentration is relatively high, it can apply large stress to the capacitor dielectric film of the capacitor due to its small water content. Accordingly, the spontaneous polarization characteristic of the capacitor dielectric film can be improved, resulting in improving the characteristics of the capacitor. As a result, a semiconductor device including a highly reliable capacitor can be realized.
The first semiconductor device preferably further comprises a hydrophobic primer layer formed on a surface of the protection film.
Thus, the first TEOS-O3 film is formed on the protection film having a hydrophobic surface and hence can be satisfactorily grown to attain good step coverage. Accordingly, the step coverage of an interlayer insulating film formed on the capacitor can be improved, so as to improve the insulating property and the surface planeness of the interlayer insulating film.
The first semiconductor device preferably further comprises an underlying oxide film formed, between the protection film and the first TEOS-O3 film, from a silicon oxide film including no impurity or a silicon oxide film including at least one of boron and phosphorus.
Thus, the first TEOS-O3 film is formed on the underlying oxide film having no dependency on an underlying film and good conformability with a TEOS-O3 film. Therefore, even when underlying films of different materials, such as an interconnection layer and a protection film, are present below the first TEOS-O3 film, the first TEOS-O3 film can be satisfactorily grown without being affected by these underlying films, resulting in attaining a uniform thickness.
When the first semiconductor device includes the underlying oxide film, it preferably further comprises a hydrophobic primer layer formed on a surface of the underlying oxide film.
Thus, the first TEOS-O3 film is formed on the underlying oxide film having a hydrophobic surface, and hence, it can be satisfactorily grown to attain good step coverage. Accordingly, the step coverage of an interlayer insulating film formed on the capacitor can be improved, so as to improve the insulating property and the surface planeness of the interlayer insulating film.
The second semiconductor device of this invention comprises a capacitor including a capacitor lower electrode, a capacitor dielectric film of a highly dielectric film or a ferroelectric film and a capacitor upper electrode successively formed on a semiconductor substrate; a protection film formed on the semiconductor substrate over the capacitor; an underlying oxide film formed, on the protection film, from a silicon oxide film including no impurity or a silicon oxide film including at least one of boron and phosphorus; and a TEOS-O3 film formed on the underlying oxide film.
In the second semiconductor device, the TEOS-O3 film is formed on the underlying oxide film having no dependency on an underlying film and good conformability with a TEOS-O3 film. Therefore, even when underlying films of different materials, such as an interconnection layer and a protection film, are present below the TEOS-O3 film, it can be satisfactorily grown without being affected by these underlying films. As a result, an interlayer insulating film can be formed in a uniform thickness. Accordingly, a semiconductor device including a stable and long-lived capacitor can be realized.
The second semiconductor device preferably further comprises a hydrophobic primer layer formed on a surface of the underlying oxide film.
Thus, the TEOS-O3 film is formed on the underlying oxide film with a hydrophobic surface, and hence, it can be satisfactorily grown to attain good step coverage. Accordingly, the step coverage of an interlayer insulating film formed on the capacitor can be improved, so as to improve the insulating property and the surface planeness of the interlayer insulating film.
The first method of fabricating a semiconductor device of this invention comprises the steps of forming, on a semiconductor substrate, a capacitor including a capacitor lower electrode, a capacitor dielectric film of a highly dielectric film or a ferroelectric film and a capacitor upper electrode; forming, on the semiconductor substrate, a protection film over the capacitor; forming, on the protection film, a first TEOS-O3 film through first TEOS-O3 CVD where an ozone concentration is relatively low; and forming, on the first TEOS-O3 film, a second TEOS-O3 film through second TEOS-O3 CVD where the ozone concentration is relatively high.
In the first method of fabricating a semiconductor device, the first TEOS-O3 film is formed on the protection film covering the capacitor through the first TEOS-O3 CVD where the ozone concentration is relatively low. Therefore, the first TEOS-O3 film can attain good film quality with no defects such as holes and good adhesion to the protection film due to its large water content. Also, since the second TEOS-O3 film is formed through the second TEOS-O3 CVD where the ozone concentration is relatively high, it can apply large stress to the capacitor dielectric film of the capacitor due to its small water content. Accordingly, the spontaneous polarization characteristic of the capacitor dielectric film can be improved, so as to improve the characteristics of the capacitor. As a result, a semiconductor device including a highly reliable capacitor can be fabricated.
The first method of fabricating a semiconductor device preferably further comprises, between the step of forming the protection film and the step of forming the first TEOS-O3 film, a step of forming a hydrophobic primer layer on a surface of the protection film by supplying a hydrophobic primer agent onto the protection film.
Thus, the first TEOS-O3 film is formed on the protection film having a hydrophobic surface, and hence, it can be satisfactorily grown to attain good step coverage. Accordingly, the step coverage of an interlayer insulating film formed on the capacitor can be improved, so as to improve the insulating property and the surface planeness of the interlayer insulating film.
The first method of fabricating a semiconductor device preferably further comprises, between the step of forming the protection film and the step of forming the first TEOS-O3 film, a step of forming, on the protection film, an underlying oxide film from a silicon oxide film including no impurity or a silicon oxide film including at least one of boron and phosphorus.
Thus, the first TEOS-O3 film is formed on the underlying oxide film having no dependency on underlying films and good conformability with a TEOS-O3 film. Therefore, even when underlying films of different materials, such as an interconnection layer and a protection film, are present below the first TEOS-O3 film, it can be satisfactorily grown without being affected by these underlying films, resulting in attaining a uniform thickness.
When the first method of fabricating a semiconductor device includes the step of forming the underlying oxide film, it preferably further comprises, between the step of forming the underlying oxide film and the step of forming the first TEOS-O3 film, a step of forming a hydrophobic primer layer on a surface of the underlying oxide film by supplying a hydrophobic primer agent onto the underlying oxide film.
Thus, the first TEOS-O3 film is formed on the underlying oxide film having a hydrophobic surface, and hence, it can be satisfactorily grown to attain good step coverage. Accordingly, the step coverage of an interlayer insulating film formed on the capacitor can be improved, so as to improve the insulating property and the surface planeness of the interlayer insulating film.
In the first method of fabricating a semiconductor device, the ozone concentration in the first TEOS-O3 CVD is preferably 25 g/m3 or less and the ozone concentration in the second TEOS-O3 CVD is preferably 130 g/m3 or more.
In this manner, the first TEOS-O3 film formed through the first TEOS-O3 CVD can attain a good self-reflow characteristic, and hence can be free from imperfections such as defects. Accordingly, the first TEOS-O3 film can attain good film quality. Also, the second TEOS-O3 film formed through the second TEOS-O3 CVD can apply sufficient stress to the capacitor dielectric film of the capacitor and prevent cracks derived from its small water content from being caused therein during a heat treatment.
In the first method of fabricating a semiconductor device, the first TEOS-O3 CVD is preferably carried out with a value of (a flow rate of ozone/a flow rate of TEOS) set to 3 or less, and the second TEOS-O3 CVD is preferably carried out with the value of (a flow rate of ozone/a flow rate of TEOS) set to 15 or more.
In this manner, the first TEOS-O3 film formed through the first TEOS-O3 CVD can attain a good self-reflow characteristic, and hence can be free from imperfections such as defects. Accordingly, the first TEOS-O3 film can attain good film quality. Also, the second TEOS-O3 film formed through the second TEOS-O3 CVD can apply sufficient stress to the capacitor dielectric film of the capacitor and prevent cracks derived from its small water content from being caused therein during a heat treatment.
In the first method of fabricating a semiconductor device, the second TEOS-O3 film preferably has tensile stress of 1xc3x97102 N/cm2 through 4xc3x97104 N/cm2.
Thus, the second TEOS-O3 film can apply sufficient stress to the capacitor dielectric film of the capacitor, so as to improve the spontaneous polarization characteristic of the capacitor dielectric film. As a result, the characteristics of the capacitor can be improved.
In the first method of fabricating a semiconductor device, the second TEOS-O3 CVD is preferably carried out at a temperature of 350xc2x0 C. through 450xc2x0 C.
Thus, the second TEOS-O3 film can be subjected to a heat treatment carried out at a high temperature. Therefore, the stress of the second TEOS-O3 film can be increased and the density of the second TEOS-O3 film can be increased through the heat treatment carried out at a high temperature. As a result, the characteristics of the capacitor can be further improved.
The first method of fabricating a semiconductor device preferably further comprises a step of conducting a plasma treatment on a surface of the second TEOS-O3 film.
Thus, a hardening layer with a thickness of approximately several nm can be formed on a surface of the second TEOS-O3 film, so as to improve the ability to disperse the water content of the second TEOS-O3 film.
In this case, the plasma treatment is preferably plasma coating or plasma sputtering etching using plasma of a gas including at least one of a N2 gas, a NH3 gas, a N2O gas, an O2 gas, an Ar gas, a Cl2 gas and a C2F6 gas.
Thus, a hardening layer with a thickness of approximately several nm can be definitely formed on a surface of the second TEOS-O3 film.
The first method of fabricating a semiconductor device preferably further comprises a step of forming a silicon nitride layer on a surface of the second TEOS-O3 film by conducting a plasma treatment on the second TEOS-O3 film.
Thus, the water content of the second TEOS-O3 film can be prevented from diffusing into the capacitor dielectric film and the water content in the air can be prevented from diffusing into the second TEOS-O3 film because the silicon nitride film has high ability to prevent diffusion of water content.
The second method of fabricating a semiconductor device of this invention comprises the steps of forming, on a semiconductor substrate, a capacitor including a capacitor lower electrode, a capacitor dielectric film of a highly dielectric film or a ferroelectric film and a capacitor upper electrode; forming a protection film on the semiconductor substrate over the capacitor; forming, on the protection film, an underlying oxide film from a silicon oxide film including no impurity or a silicon oxide film including at least one of boron and phosphorus; and forming a TEOS-O3 film on the underlying oxide film.
In the second method of fabricating a semiconductor device, the TEOS-O3 film is formed on the underlying oxide film having no dependency on underlying films and good conformability with a TEOS-O3 film. Therefore, even when underlying films of different materials, such as an interconnection layer and a protection film, are present below the TEOS-O3 film, it can be satisfactorily grown without being affected by the underlying films. As a result, an interlayer insulating film can be formed in a uniform thickness. Accordingly, a semiconductor device including a stable and long-lived capacitor can be fabricated.
In the second method of fabricating a semiconductor device, the protection film is preferably a silicon oxide film including no impurity or a silicon oxide film including at least one of boron and phosphorus formed by TEOS-O3 CVD.
Thus, the protection film can attain tensile stress, and hence, the spontaneous polarization of the capacitor dielectric film of the capacitor formed on the protection film can be further accelerated and the surface planeness of the protection film can be improved. Accordingly, the capacitor can attain stability and a long life.
The second method of fabricating a semiconductor device preferably further comprises, between the step of forming the underlying oxide film and the step of forming the TEOS-O3 film, a step of forming a hydrophobic primer layer on a surface of the underlying oxide film by supplying a hydrophobic primer agent onto the underlying oxide film.
Thus, the TEOS-O3 film is formed on the underlying oxide film having a hydrophobic surface, and hence, it can be satisfactorily grown to attain good step coverage. Accordingly, the step coverage of an interlayer insulating film formed on the capacitor can be improved, so as to improve the insulating property and the surface planeness of the interlayer insulating film.
When the first or second method of fabricating a semiconductor device includes the step of forming the hydrophobic primer layer, the primer agent is preferably hexamethyldisilazane.
Thus, the surface of the protection film or the underlying oxide film can be definitely made hydrophobic.
In the second method of fabricating a semiconductor device, the TEOS-O3 film is preferably formed through TEOS-O3 CVD where an ozone concentration is 130 g/m3 or more.
Thus, the TEOS-O3 film can attain a good self-reflow characteristics, so as to be free from imperfections such as defects. Therefore, the TEOS-O3 film can attain good film quality.
In the second method of fabricating a semiconductor device, the TEOS-O3 film is preferably formed through TEOS-O3 CVD where a value of (a flow rate of ozone/a flow rate of TEOS) is set to 15 or more.
Thus, the TEOS-O3 film can apply sufficient stress to the capacitor dielectric film of the capacitor and can prevent cracks derived from its small water content from being caused therein during a heat treatment.
The second method of fabricating a semiconductor device preferably further comprises a step of conducting a plasma treatment on a surface of the TEOS-O3 film.
Thus, a hardening layer with a thickness of approximately several nm is formed on a surface of the TEOS-O3 film, so as to improve the ability to prevent diffusion of the water content of the TEOS-O3 film.
In this case, the plasma treatment is preferably plasma coating or plasma sputtering etching using plasma of a gas including at least one of a N2 gas, a NH3 gas, a N2O gas, an O2 gas, an Ar gas, a Cl2 gas and a C2F6 gas.
Thus, a hardening layer with a thickness of approximately several nm can be definitely formed on a surface of the TEOS-O3 film.
The second method of fabricating a semiconductor device preferably further comprises a step of forming a silicon nitride layer on a surface of the TEOS-O3 film by conducting a plasma treatment on the TEOS-O3 film.
Thus, the water content of the TEOS-O3 film can be prevented from diffusing into the capacitor dielectric film and the water content in the air can be prevented from diffusing into the TEOS-O3 film because the silicon nitride film has high ability to prevent diffusion of the water content.
The system for fabricating a semiconductor device of this invention comprises a chamber including a substrate holder for holding a semiconductor substrate; TEOS-O3 supply means for supplying, to the inside of the chamber, a mixture of gaseous TEOS and an ozone gas; and primer agent supply means for supplying, to the inside of the chamber, a hydrophobic gaseous primer agent.
The system for fabricating a semiconductor device of this invention thus includes the primer agent supply means for supplying the hydrophobic gaseous primer agent to the inside of the chamber. Therefore, a hydrophobic primer layer can be formed on a surface of an underlying film, such as a protection film or an underlying oxide film, formed below a TEOS-O3 film. Accordingly, a TEOS-O3 film with good step coverage can be grown.
In the system for fabricating a semiconductor device, the primer agent is preferably hexamethyldisilazane.
Thus, the surface of the underlying film such as a protection film or an underlying oxide film can be definitely made hydrophobic.
The system for fabricating a semiconductor device preferably further comprises means for supplying, to the inside of the chamber, a mixture obtained by mixing the mixture supplied from the TEOS-O3 supply means with the primer agent supplied from the primer agent supply means.
Thus, after forming a hydrophobic primer layer on a surface of the underlying film such as a protection film or an underlying oxide film, a TEOS-O3 film can be grown on the primer layer. Therefore, a TEOS-O3 film with good step coverage can be formed with high mass-productivity.
In the system for fabricating a semiconductor device, the TEOS-O3 supply means preferably has means for changing the gaseous TEOS into mist and mixing the mist with the ozone gas.
Thus, even when the ozone concentration in TEOS-O3 CVD is low, a TEOS-O3 film can be grown. Therefore, a TEOS-O3 film having good film quality free from defects such as holes and having a large water content can be formed.
In the system for fabricating a semiconductor device, the TEOS-O3 supply means preferably has means for charging the mist obtained from the gaseous TEOS with electricity.
Thus, the mist obtained from the TEOS can be charged with electricity, and hence, the growth rate of the TEOS-O3 film can be improved and the thickness of the TEOS-O3 film can be increased.
In this case, the substrate holder preferably has means for applying, to the semiconductor substrate, a polarity reverse to a polarity of electricity with which the mist is charged.
Thus, the charged TEOS mist can be electrostatically adsorbed onto the surface of the semiconductor substrate, and hence, the growth rate and the thickness of the TEOS-O3 film can be further increased.